Distinct Properties of the XY Pseudoautosomal Region Crucial for Male Meiosis

Abstract

Meiosis requires that each chromosome finds its homologous partner and undergoes at least one crossover. X-Y chromosome segregation hinges on efficient crossing-over in a very small region of homology, the pseudoautosomal region (PAR). We find that mouse PAR DNA occupies unusually long chromosome axes, potentially as shorter chromatin loops, predicted to promote double-strand break (DSB) formation. Most PARs show delayed appearance of RAD51/DMC1 foci, which mark DSB ends, and all PARs undergo delayed DSB-mediated homologous pairing. Analysis of Spo11β isoform-specific transgenic mice revealed that late RAD51/DMC1 foci on the PAR are genetically distinct from early PAR foci and global foci, and that late PAR foci promote efficient X-Y pairing, recombination and male fertility. Our findings uncover specific mechanisms that surmount the unique challenges of X-Y recombination.

A non-mosaic isodicentric Y chromosome resulting from breakage and fusion at the Yq pseudo-autosomal region in a fetus

“…Emerging evidence also suggested higher rates of problem behaviors and hyperactive/impulsive symptoms [18]. Considering important role of pseudo-autosomal region of meiotic sex chromosome pairing and intact pseudo-autosomal regions (PARs) in this case, it is anticipated the meiotic paring would not be compromised [19].…”

Superresolution imaging reveals structurally distinct periodic patterns of chromatin along pachytene chromosomes

“…We imaged chromosome spreads here, and the situation might differ in structurally preserved nuclei. Several publications have shown lateral extensions of meiotic chromosomes that are commonly believed to be loops (31,32). The validity of measuring loop sizes using our newly developed DNA labeling technique could be tested on cohesin mutant Smc1b −/− (structural maintenance of chromosomes protein 1B) meiocytes, in which loops are known to be larger (32).…”

Parental epigenetic control of embryogenesis: a balance between inheritance and reprogramming?

“…These chromosomes are held together during meiotic prophase by the formation of a single crossover at X-Y homologous sequences known as the pseudoautosomal region [99]. The unpaired regions of the chromosomes form a sub-domain on the nuclear periphery termed the sex body where they undergo transcriptional silencing in a process known as MSCI (meiotic sex chromosome inactivation) [100].…”